Hardened, disk-shaped machine parts are frequently used in bearing technology in general. For example, rotor disks for axial roller and sleeve bearings, mounting disks, rings for separating rows of rolling elements and rolling bearings and the like, are usually made from precision steel and are then hardened and finally finished to produce the geometrically dimensioned surfaces within prescribed tolerances. It has been found that during the hardening process and particularly in the cooling phase after hardening, internal stresses develop in the material which produce distortion of the shape which, except for minor deviations, is satisfactory subsequent to soft processing. In view of this deviation it is, therefore, necessary to provide for substantially dimensional allowances in order to arrive at the desired quality by hard processing. It is, therefore, desirable to maintain so-called hardening distortion to a minimum. To achieve this, it has already been proposed that the machine parts be mounted in a die during hardening. This process, however, is extremely expensive since each machine part must be handled individually. As a practical matter, it has been determined that this expense is prohibitive particularly in the case of small machine parts.
West German Pat. No. 2,304,557 also discloses a method for subjecting the surface of steel bars to a pressure polishing process so that they retain their cylindrical shape during hardening. It has been found, however, that when this process is used for disk-shaped, relatively thin machine parts, the results are not satisfactory by reason of the fact that these disks after processing exhibit either a wavy or conical form of distortion.